Assessment of the value of 6-min walk test to predict the severity of interstitial lung disease among Indian patients

Abstract

Introduction: The prevalence of interstitial lung disease (ILD) is increasing. High-resolution computerized tomography (HRCT), despite having limitations, remains the choice of method for diagnosis and assessment of severity of ILD. Objective: To determine the efficacy of 6-min walk test to assess the severity of the ILD compared to HRCT. Methodology: A cross-sectional study was done among 40 patients with ILD in a tertiary hospital in Hyderabad. The data included age, gender, smoking, HRCT, 6-min walk test, spirometry, diffusion lung capacity and medical history. Mann–Whitney U test, Kruskal–Wallis test, and ROC curve were used to determine the outcomes. Results: The mean age of participants was 57.18 + 13.01 years. 62.5% never smoked. Overall, 50% had severe ILD, and the rest had mild to moderate. The distance walked per 6-min, SpO2 before and SpO2 after, was significantly lower (p = 0.001; 0.002; <0.001, respectively) among patients with severe ILD than mild or moderate. The sensitivity and 1-specificity of the distance walked in 6-min to detect the severity of ILD was 0.90 and 0.31, respectively; sensitivity and 1-specificity of SpO2 before the test was 0.81 and 0.34, while that of SpO2 after the test was 0.90 and 0.17, respectively. Conclusion: This study found that the 6-min walk test is highly sensitive and specific for predicting the severity of ILD among patients. All three components of the 6-min walk test: distance, oxygen saturation before, and oxygen saturation after the test significantly lowered and were independent predictors of severe ILD.